Stroke is a leading cause of adult disability in the United States, with upper motor deficits being the primary result of the disability. These motor disabilities greatly affect quality of life for the patient and their loved ones. In addition, the loss of motor function exacts a financial toll on the healthcare system of nearly $70 billion yearly. Patients with hemiplegia or hemiparesis generally regain walking without the use of an assistive device while only half to one-third of patients regain some degree of use of their upper extremity, even after intensive rehabilitation therapy. The severe functional impairment affects occupational performance, and as a result, few stroke victims are able to return to work. Upper limb motor disabilities from stroke have an unfavorable effect on the activities of daily living critically affecting the quality of life for the stroke victim as well as family members and caregivers.
Physical rehabilitation can result in significant improvements in motor outcomes after stroke. Improvements in recovery of upper extremity function have also been reported for electromyographic feedback, motor imagery, robotics, and repetitive task practice, though large scale clinical trials have yet to be implemented. Unfortunately for most patients, the gains are not enough to have a large impact on daily living. Further, current rehabilitative therapies, such as constraint-induced movement therapy, are restricted to individuals with mild to moderate deficits. Few options are available for those stroke survivors with moderate to severe deficits. Therefore, there is still a tremendous need for methods that improve recovery of function even further.
To enhance recovery further, adjuvant therapies have been tried. For example, amphetamines can be effective at enhancing recovery of motor abilities beyond that seen with physical rehabilitation alone; however, even the positive results for motor outcomes are only incremental, and amphetamine use has many well-known side effects. Several small, randomized controlled trials have shown that epidural stimulation significantly improves motor recovery in animal models and in human stroke survivors. Unfortunately, the method requires brain surgery associated with the potential for significant complications and is not likely to reach widespread clinical use in stroke patients. Also, a recent randomized clinical trial failed to demonstrate improved efficacy compared with intensive physical rehabilitation.
Less invasive methods for cortical stimulation have also been combined with physical rehabilitation. Again, however, while real gains in function are observed, the gains are modest, for the most part. Thus, a great need still exists for a method to improve motor function further.
Current rehabilitation techniques do not sufficiently restore lost function in many individuals. Statistically significant improvements to motor deficits can be induced even several months after stroke. However, these improvements do not consistently improve quality of life for the vast majority of patients and their caretakers, thus greater improvements in motor skills are needed following rehabilitation.
Motor therapies typically involve practicing either fine motor or gross motor skills. Repetition is generally the mechanism of the therapies. In some variations, such as constraint therapy and mirror therapy, other mechanisms are engaged.
Some examples of typical motor therapies may be actions such as: squeezing a dynamometer, turning on/off a light switch, using a lock and key, opening and closing a door by twisting or depressing different doorknobs, flipping cards, coins and other objects over, placing light and heavy objects at different heights, moving pegs to hole and remove pegs from hole, lifting a shopping basket/briefcase, drawing geometric shapes, dressing, typing, reaching and grasping light and heavy objects, grasping and lifting different (size, shape, and texture) objects, doing a precision grasp, writing, drawing connect the dots, opening and closing a jar or medication bottle, lifting an empty and full cup/glass, using feeding utensils, cutting food, stirring liquids, scooping, pouring a glass of water with the paretic hand; or using the paretic hand to stabilize the glass and pouring with the good hand, picking an object and bring to target, using a spray can, cutting with scissors, or brushing teeth/hair.
U.S. Pat. No. 6,990,377 (Gliner, et al.) describes a therapy to treat visual impairments. The therapy includes presenting various types of visual stimuli in conjunction with stimulation of the visual cortex. The therapy described in Gliner does not control the timing relationship of the stimuli and the stimulation.
U.S. Patent Application Publication 2007/1079534 (Firlik, et al.) describes a therapy having patient interactive cortical stimulation and/or drug therapy. The therapy has patients performing tasks, detecting patient characteristics and modifying the stimulation depending on the detected patient characteristics. The therapy described in Firlik does not control the timing relationship between the tasks and the cortical stimulation.
It is common in the prior art to suggest that stimulation of the cortex, the deep brain, the cranial nerves and the peripheral nerves are somehow equivalent or interchangeable to produce therapeutic effects. Despite these blanket statements, stimulation at different parts of the nervous system is not equivalent. It is generally understood that the vagus nerve is a nerve that performs unique functions through the release of a wide array of neuromodulators throughout the brain. To generate certain kinds of plasticity, the timing of the stimulation of the vagus nerve is critical in producing specific therapeutic effects.
U.S. Pat. No. 6,104,956 (Naritoku, et al.) is representative of work done using vagus nerve stimulation (VNS) to treat a variety of disorders, including epilepsy, traumatic brain injury, and memory impairment. The VNS is delivered without reference to any other therapy. To improve memory consolidation, VNS is delivered several minutes after a learning experience. Memory consolidation is unrelated to the present therapy for treating motor deficits.